*4.3. Gel Film Preparation*

The CH-gel film-forming solution was made in the manner described by Siripatrawan and Harte [29], with minor modifications. A number of initial experiments were carried out to determine the best type and amount of acid solvent and plasticizer to be utilized in the preparation of CH-based gel films. The findings showed that 2% CH in 1% acetic acid might be used to create the best CH-gel films. The findings also showed that the addition of glycerol as a plasticizer at a percentage of 30% w/w of CH powder enhanced the mechanical characteristics of the films. Hundred millilitres of glacial acetic acid solution (1%) and CH powder (2 g) (deacetylation degree: 75%, Sigma Aldrich Company, Darmstadt, Germany) were combined to create a film-forming solution. The film-forming solution was supplemented with glycerol (El-Gomhoria Chemical Co., Tanta, Egypt), a plasticizer, at a fixed percentage of 30% weight/weight of CH. The resulting solution was then heated in a water bath shaking incubator for 30 min at 60 ◦C and 100 rpm. To get rid of undissolved contaminants, the chitosan solution was then filtered using a coarse sintered glass filter. After being cooled to ambient temperature, the EPPE was mixed into the film-forming solution to produce percentages of 0, 1, 3, and 5% (*w*/*v*). The resultant solutions were homogenized with a Moulinex homogenizer (Courneuve, France). After that, a sonicator (Singen, Germany) was used to degas the film-forming solutions to get rid of air bubbles. A ceramic plate was used to cast each film-forming solution, and it was allowed to dry there. Prior to testing, the films were conditioned for 48 h at 25 ◦C and 50% RH in a chamber.
